1. Field of the Invention
The present invention relates to a plug terminator having electrical contacts therein, each contact being connectable to one of a multiplicity of electrical conductors, and in particular, to a terminator having a projecting ground structure therein arranged to isolate each electrical contact. In addition, the present invention relates to a receptacle structure useful with such plug terminator.
2. Description of the Prior Art
As the performance of electronic devices has increased exponentially it has become recognized in the art that the transmission of electrical signals, whether within a given electronic apparatus or between coupled apparatuses, must be approached from a system viewpoint. Such a viewpoint mandates that not only must each individual component in the signal transmission system be optimized for high speed operation, but also the interfaces between components in the transmission system must be able to perform interactively without degrading the performance of an adjacent component.
One of the first components in the signal transmission system to receive attention is the transmission cable itself. The realization has been made that the cable handling the high speed signals is the electrical equivalent of a transmission line in that it extends an electrically great distance with respect to the wavelength of the transmitted signals. This is true even though in most instances the cable extends only a physically short distance between components of a given apparatus or between cooperating apparatus.
The design of electrical cable has advanced to a point wherein the cable can be precisely engineered to exhibit predetermined electrical properties. Exemplary of such cable structure is the flat cable and the round cable respectively disclosed and claimed in U.S. Pat. No. 4,800,236 (Lemke), and in U.S. Pat. No. 4,920,234 (Lemke), both assigned to the assignee of the present invention. The cables disclosed in these last-mentioned patents include a corrugated ground structure which defines separate enclosed regions, or envelopes, which extend throughout the entire length of the cable. Each of the envelopes receives one or more ordinary jacketed conductors. When the ground structure is connected to a predetermined electrical potential the conductor in each envelope is isolated from those conductors disposed in adjacent envelopes. As a result such a cable exhibits electrical properties closely similar to those attainable from coaxial cable despite the fact that only ordinary jacketed conductors are utilized.
The system viewpoint has expanded to include considerations of electrical performance in the transition region intermediate the end of the cable and the cable terminator. The connector structure disclosed and claimed U.S. Pat. No. 4,731,031 (Lemke), assigned to the assignee of the present invention, utilizes a ground plane spaced predetermined distances from the ends of the conductors in the cable, from the contacts in the connector, and from the interconnection therebetween, for the purpose of minimizing electrical discontinuities in the system.
Density of the terminator, that is, the number of signals that can pass through a given terminator, is also an important consideration. In conventional systems attempts have been made to extend the shielding and control the impedance of the system beyond the transmission line by simply dedicating alternating contacts in the linear array of contacts in the terminator as ground contacts. The contact is not physically altered, but is merely designated as a ground contact and connected to a predetermined ground potential. The net result of these factors is that the density of the terminator is limited.
The plug terminator disclosed and claimed in U.S. Pat. No. 4,824,383 (Lemke) (EL-4271-B), issued Apr. 25, 1989, extends the system concept to the individual terminator of the transmission system in a way that increases the density of the terminator. The terminator shown in this last mentioned patent is adapted for use with either a multiple conductor cable or a multiple tracing substrate and is thus adapted to interconnect in substrate-to-substrate, cable-to-cable, or cable-to-substrate form. This terminator includes structure that serves to electrically isolate individual or groups of contact elements in the terminator to prevent or to minimize cross talk between adjacent conductors and to prevent or minimize degradation of signal transmission. The isolating structure in the terminator is such that the contacts need not themselves be included as part of the isolating structure, whereby the signal density of the terminator may be increased.
The terminator includes a metallic ground structure which electrically isolates individual or groups of adjacent electrical contact elements disposed on or in a contact support member of the terminator. The ground structure has a baseplate with at least one wall that extends upwardly from a working surface of the baseplate. In the preferred case one or more walls also extend from the opposite working surface of the baseplate. The wall(s) define(s) a plurality of channels that extend in side-by-side relationship across the surface of the baseplate.
The insulated support member has a body portion with an array of extending fingers. The insulated support member is mounted on the baseplate with the fingers thereof extending into the channels on the baseplate. A single electrical contact element or a plurality of such contact elements is mounted on each of the fingers. In one arrangement the fingers may be provided with a recess in which an individual contact or a group of contacts is disposed.
The walls on the baseplate walls extend above the baseplate for a greater distance than do the electrical contacts. As a result, with the ground structure connected to a predetermined potential, each of the individual contacts or each group of contacts is electrically isolated from the adjacent contact or group of contacts, as the case may be, thus preventing or minimizing cross talk therebetween.